1. Field of the Invention
The present invention relates to a hybrid integrated circuit device which includes a memory cell which is capable of having data electrically written therein and a circuit element which writes the data in the memory and reads the data from the memory both disposed on a circuit board.
2. Description of Related Art
FIG. 11 is a circuit diagram illustrating a part of conventional hybrid integrated circuit device. An EPROM 2 has a memory cell, which electrically stores data such as programmed data therein and a circuit element such as an integrated circuit (IC) 3 consisting of circuits including a microcomputer which writes the data in the EPROM 2 and reads the data from the EPROM 2 disposed on a circuit board 1. As shown in FIG. 11, the EPROM 2 is integrated in the IC 3.
When the data are written in the EPROM 2 after hybrid integrated circuits are disposed on the circuit board 1, a high voltage V.sub.PP for writing the data (writing voltage) is supplied to the EPROM 2 via an outer terminal B and a power terminal 3a of the IC 3, and also an active voltage V.sub.DD is supplied to the IC 3 via an outer terminal A and a power terminal 3b. When the data written in the EPROM 2 are read from the EPROM 2 after the circuit board 1 is packaged, a reading voltage used for reading the data is supplied to the EPROM 2 via the outer terminal B and the power terminal 3a, and also the logic power is supplied to the IC 3 via the outer terminal A and the power terminal 3b. In this case, the reading voltage is the same voltage as the voltage V.sub.DD of the IC 3.
Recently, because functions of the hybrid integrated circuit device are improved, the number of outer terminals of the hybrid integrated circuit device have increased. However, if the outer terminals of the hybrid integrated circuit device increase, the area of the circuit board also increases, thus, the number of outer terminals of the hybrid integrated circuit must be decreased in order to reduce the area of the circuit board.
Because the writing voltage must be higher than the reading voltage and the voltage V.sub.DD, as shown in FIG. 11, the outer terminal B is necessary to supply the writing voltage to the EPROM 2. In this case, if the data are written in the EPROM 2 before the hybrid integrated circuits are disposed on the circuit board 1, and the reading voltage is supplied to EPROM 2 from a power source area other than the outer terminal B, for instance, the reading voltage is supplied to the EPROM 2 from the V.sub.DD terminal, the outer terminal B used for writing the data is not necessary. However in this case, it takes many hours to complete the writing of the data in the EPROM 2 of this hybrid integrated circuit device; thus, there is little advantage to this type of EPROM 2.